Since there is talk about storage, I am curious myself on the experience of others.
Knowing external hard drives have the possibility of failure in the future, and at times even for amateurs the need for firewire over a cheaper usb alternative doesn't cut it, the convenience of wanting a mirror drive to back up files, and the backing of a reputable brand (LaCie or Western Digital?)...the costs easily add up. I am currently using western digital firewire 800 studio versions that are 2TB or 1TB (after mirrored) and they are running just under $200 each and I am hesitant to buy a cheaper brand/model and possibly put my image library at risk - what have you guys been doing? On a side note I'd say for almost the 3rd year I've used a 5d2 as an amateur, I am currently on my 2nd 2tb/1tb studio drive.
On another note of megapixels increase, there is that issue to those that choose to do a little heavier post processing (DxO, photomatix, photoshop/layering/panos?, etc). I also don't like to batch process my images and go through them individually. With my current desktop setup of a 3.0ghz quadcore and 8gigs of ram, I have noticed increased processing times and occasional freezing in my work flow (after making the step up from a 5d to 5d2). I am hesitant on how my current setup will hold up to a 36+mp raw file size for post processing.
It's not the resolving power of lenses which is the problem, it's the border & corner performance. On a 12MP camera it's much less noticeable as the resolution across the frame is more or less uniform, it becomes an issue though as the MP count increases. The 5D MkII using a 17 - 40mm F/4 at the wide end wide open really shows this problem - plenty of resolution in the centre, no measureable resolution at all in the corners, it's a dramatic fall off which is really noticable. Up the MP count higher and it'll become even more noticeable as centre performance increases, while border & edge stays the same.
I've noticed this too and the corner sharpness has been a big issue for me. Stopping down to f/16 with the trade off of diffraction is not cutting it for me either. I am sincerely hoping for some new ultra wide lens designs to improve corner performance - hopefully in a 14-24 zoom focal range!
You're paying a bit much at $200 each for your 2TB externals. I've been eying a set of internal Hitachi Deskstar 3tb drives that come in at just under 200 each. Their 2tb equivalent drives are 120 dollars, each. You can have a mirrored backup external setup for under 300 if you go with something like this:http://www.newegg.com/Product/Product.aspx?Item=N82E16817153112
300 is a lot of money but, is parsimonious in comparison to the cost of the camera you shoot with.
Western's drives (and whatever Lacie uses), don't have monopolies on reliability. I use mostly Western but, I also have Seagate drives, both of which have failed on me at some time in the past. I usually buy whatever meets the specs I need and, has decent reviews at a reputable retailer like newegg or zipzoomfly. Avoid individual drives (not manufacturers) with a known QC problem and make sure to back up your data regularly. That's the best insurance against failure, far better than sticking with a particular brand of drive.
My workflow isn't as detailed as yours is as I'm very much a newbie. But, I'm using Lightroom and GIMP on an ancient overclocked Opteron 165 with a paltry 2 gigs of RAM. I don't have issues with freezing while editing a single image at one time or, batch processing a whole bunch of photos. I shoot with a 60D. I doubt the extra 3 megapixels would take a much better bit of hardware to its knees simply because of the increased load. I'd wager that your instability issue is a software problem, not a hardware one.
Having said that, I will still upgrade my computer, mostly because it's nearly 6 years old and the hardware doesn't function like it used to. That, and I need to build a flexible backup NAS to insure all the music, video, pictures and data I've accumulated over the years.
Edit: With the NAS, I'll have 6tb of redundant storage space. One copy on my workstation, one copy on my NAS. The most important data (financial information, personal documents, music and photos) with be triple redundant with a second local copy at my work station. Aside from a ravaging house fire, I don't see my data going anywhere for decades to come (knock on wood).